The discussion below is merely provided for general background information and is not intended to be used as an aid in determining the scope of the claimed subject matter.
It is common to provide filtering of power electronic amplifiers in order to remove high frequency elements therein. One common approach is to use a LC (inductor-capacitor) in the output stage across which the output power for the load is obtained. Although such a filter is effective in removing high frequency components, a problem arises if the resonant frequency of the LC filter is in the operational range of the power amplifier. In such cases, an undesirable large voltage can develop across the load at the resonant frequency. Thus, a method of damping the natural response of the LC filter to prevent unwanted and excessive load voltage is necessary.
Various approaches of damping have been used. In a first form, damping is provided by using a dissipative approach, generally in the form of a resistor or a combination of a resistor and a capacitor. However, this approach results in unnecessary and potentially high levels of power dissipation. In an alternative approach, active damping is used. However, active damping requires the use of a control loop and therefore, a method of sensing the output voltage.
Two known methods of sensing output voltage have been used. The first method requires the use of high impedance resistors and a differential operational amplifier. However, this method does not provide galvanic isolation, and therefore can result in limited or even prohibited use in circuits requiring a high level of electrical isolation. A second known method requires the use of relatively expensive and electrically complex Hall Effect, or a similar type close-loop current sensor. In this method, the current sensor is configured to measure the current flowing through a resistor disposed across the terminals of a voltage signal to be measured. The current measurement is proportional to the voltage of interest. Drawbacks of this second approach include high cost and complexity.